Joining 2 streams from same object in java

Stream.concat(sOne.stream(), sTwo.stream())

You should just be aware that this drops some characteristics IIRC in some cases.

You can combine them using:

List<A> aList = ...;

Stream<String> stream = aList.stream()
                             .flatMap(a -> Stream.concat(
                                      a.getsOne().stream(), 
                                      a.getsTwo().stream())
                              );